With the advances in biotechnology, biopharmaceuticals have been developed to meet unmet medical needs. However, their short in-vivo half-life requires patients to take frequent and/or large doses of these biopharmaceuticals to achieve the target therapeutic or prophylactic goal. Long intravenous therapy or frequent injection could affect the patients' quality of life. Various polymers, such as polyethylene glycol (PEG), can be conjugated to a biomolecule (e.g., protein) to enhance the half-life and biologic activity of many biomolecules (Reddy, Ann. Pharmacother. 34:915-923, 2000). Other benefits of polymer conjugation include (a) improved product stability during the manufacturing process; (b) reduced renal clearance (Fung, et al., Polym. Prepr. 38:565-566, 1997); improved tumor trageting (Yowell, et al., Cancer Treat. Rev. 28 Suppl. A:3-6, 2002); reduced antigenicity and immunogenicity (Muller, et al., Br. J. Haematol. 110:379-384, 2000; Abshire, et al., Blood 96:1709-1715, 2000); and greater tolerability (Safra, et al., Ann. Oncol. 11:1029-1033, 2000; Judson, et al., Eur. J. Cancer 37:870-877, 2001). PEGylation has been applied to human growth factors (Kim, et al., Biomaterials 23:2311-2317, 2002; Wu, et al., Protein Expr. Purif. 48:24-27, 2006), growth hormone-releasing factor (Piquet, et al., J. Chromatogr. 944:141-148, 2002), adenovirus vector (Eto, et al., Int. J. Pharm. 354:3-8, 2008) and plasmid DNA (Hosseinkhani, et al., J. Control Release, 97:157-171, 2004). Due to the benefits of PEGylation, many conjugation reaction chemistry (Roberts, et al., Adv. Drug Deliv. Rev. 54:459-476, 2002) and polymer derivatives (European Patent No. 1578841) have been developed. As the application of biomolecule-polymer conjugation increases, it is necessary to develop simple, reproducible, and scalable unit operation to meet the manufacturing needs.